Creep and shrinkage behavior of fly ash based geopolymer concrete

The manuscript presented herein is based on the investigation of the short and long term properties of fly ash based geopolymer concrete (GPC) and their link to fly ash characteristics. Fly ash (FA) exhibits a significantly different particle morphology, which impacts the mechanical properties of the resulting GPC and typically contains impurities that fluctuate from one FA source to another. A key contribution of this research work is the capturing of the variability posed by the FA stockpile with a wide range of physical, chemical, and crystallographic characteristics as a source material to select the GPC mix design. In the case of prestressed GPC application, there are concerns on prestress loss caused by elastic shortening, shrinkage, and creep. Thus, the values of mechanical strength, ultimate shrinkage strain, and creep coefficient of the GPC have to be estimated reasonably and accurately at the design stage to avoid any loss of structural capacity the premature structural failure. The test study was conducted to evaluate the mechanical strength of fly ash based geopolymer concrete. Fly ash samples from different sources were tested to see the impact of the chemical and physical properties of the FA element on the fresh and hardened properties of the GPC. Samples from 50 different power plants were collected and analyzed to develop the regression equation. The empirical model was developed to predict the flexural strength from the compressive strength, the unit weight from the density of the FA, the elastic modulus from the unit weight, and compressive strength of the GPC and the compressive strength from the chemical and physical properties of the FA. A second set of 10 FA samples was selected randomly to validate the test results. It was observed that the prediction equation is accurate within 5 to 7 percent of the experimental values. The restrained shrinkage and free shrinkage test was conducted to observe the shrinkage of the GPC. Free shrinkage of the GPC plot was compared with the available empirical model for compatibility. In this study, an apparatus was designed to determine the creep of the GPC and an effective creep testing procedure was developed and documented. Experimental results obtained from this study were compared with the available empirical models. The results obtained from this study show that the compressive strength of the GPC can be presented with reasonable accuracy by analyzing the physical and chemical property of the FA. Also, it was found that the mechanical behavior of the GPC can be predicted with the equations given in the American Concrete Institute\u27s Building Code (ACI 318, 2008) with minor modifications. Experimental results obtained from this study were compared with the available empirical models. It has been observed that the free shrinkage strain and creep compliance prediction equations for the GPC are akin to those given in the SAKATA model and GL 2000 model

Interactions between a gall–inducing wasp Trichilogaster acaciaelongifoliae (Hymenoptera: Pteromalidae) and its host plant Acacia longifolia (Fabaceae)

Sallow Wattle (Acacia longifolia subsp. longifolia) is a native Australian shrub which is an invasive weed in some parts of Australia, and internationally. A gall-forming wasp (Trichilogaster acaciaelongifoliae), also native to Australia, causes abnormal growth of tissues (galls) in Sallow Wattle. This wasp is used outside of Australia to control invasive populations of this plant species. However, in Australia, the wasp is not effective in managing the spread of Sallow Wattle. This study investigates various aspects of the relationship between the wasp and its host plant in Australian ecosystems to better understand the physiological and ecological processes involved. The study shows that this wasp is host-specific on Sallow Wattle. The feeding action of the larval wasps increase secondary plant compounds in gall tissue, which may assist the plant to defend itself chemically against other insects and microorganisms. The growth of the galls redirects resources which are otherwise used by the plant for growth and reproduction. A second insect species was found within the galls and was identified as Megastigmus sp. This second species is likely to be a parasitoid, killing the larvae of the gall-former and occupying the gall. The presence of Megastigmus sp. in Australian ecosystems may be a key factor affecting the ability of T. acaciaelongifoliae to control Sallow Wattle in its native range. The structure of galls formed by each type of gall-inducing insects is unique and the process of gall induction also varies across species. The present study has specifically examined the initiation and development of galls formed by T. acaciaelongifoliae on A. l. longifolia. Unlike other hymenopteran groups, which induce galls during oviposition, T. acaciaelongifoliae appears to form galls on A. l. longifolia via the larval feeding process. Three major stages of gall development were identified and described: induction of gall, growth and maturation of gall, and shrinking and desiccation of gall. These findings have significantly extended our current knowledge of gall induction and development by the hymenopteran group of insects. Total antioxidant capacity (TAC), total phenol (TP), and total anthocyanin (TA) were measured in galls formed by T. acaciaelongifoliae at different growth stages of galls and in other plant tissue samples of A. l. longifolia to understand the effect of gall formation on plant phytochemistry. The results indicated differences in the amounts of phytochemicals in tissue samples from galls of different growth stages of galls and between gall tissue samples and other plant samples of A. l. longifolia. The highest amount of total antioxidant capacity, total phenols and total anthocyanin were recorded in samples of early stages galls, whereas the minimum amounts of phytochemicals were in stems of A. l. longifolia. Amounts of antioxidant capacity, phenols and anthocyanin gradually declined as galls developed and larvae became less active in their feeding activity prior to pupation. It is assumed that the active feeding action of the larvae results in increased amounts of these chemicals in the early growth stages of the galls. The effect of galls formed by the wasp, T. acaciaelongifoliae on the growth and reproduction of A. l. longifolia was investigated in the native home range of both species, where the plant is invasive. Differences in the average number of phyllodes per sub-branch were found between galled and ungalled plants. Galls were also shown to affect the growth rate of branches. The number of galls correlated positively with twig mortality; and negatively with the number of seedpods per sub-branch. While galls formed by T. acaciaelongifoliae have impacts on the growth and reproduction of A. l. longifolia plants, the plant continues to invade Australian ecosystems. An experiment was conducted to investigate the host plant preference of T. acaciaelongifoliae. Ten different native host plant species (co-occurring with A. l. longifolia in the study locations) were tested in two set of experiments; a ‘free choice test’ and ‘no choice test’. The results showed that T. acaciaelongifoliae is highly host-specific on A. l. longifolia plants. Thus, it was concluded that the presence of other plant species does not explain the continued invasiveness of A. l. longifolia in Australia. A second insect species was found in the galls developed by T. acaciaelongifoliae on A. l. longifolia. The insect species has been identified as another hymenopteran from the genus Megastigmus. Since no T. acaciaelongifoliae emerged from the galls occupied by Megastigmus sp, it is proposed that Megastigmus sp. may feed upon T. acaciaelongifoliae larvae and kill them inside the galls. This might be a key factor affecting the performance of the wasp, T. acaciaelongifoliae in controlling A. l. longifolia in its native distribution. Parasitism rates of Megastigmus sp. should be investigated in future experiments.Doctor of Philosoph

Perpetrator Workplace Aggression: Development of a Perpetrator Aggression Scale (PAS)

Perpetrator workplace aggression has always been considered as a uni-dimensional construct from the uni-dimensional perspective. The most popular and widely used scale, interpersonal deviance scale (IDS; Bennett & Robinson, 2000), to assess perpetrator workplace aggression has only seven items (i.e., seven content areas), which lacks a high level of content-related and construct-related validity. Recently, researchers have suggested that perpetrator workplace aggression may be a construct with a general factor at the top (Sackett & DeVore, 2001); however, this general factor can be less clear for a more complex model (Marcus et al., 2016). Using three samples (N = 271, 337, & 264), this research found that perpetrator workplace aggression was also a uni-dimensional construct from the multi-dimensional perspective, the general factor was very clear for a complex model, and developed a new scale with a higher level of content-related (i.e., 24 different content areas of perpetrator workplace aggression) and construct-related validity (by developing a large nomological network). In addition to a higher level of content-related and construct-related validity, the new scale showed a higher level of internal consistency and substantive validity. Hence, I recommend that researchers and practitioners use this new scale in future when assessing perpetrator workplace aggression

An Effective Approach to Improving Low-Cost GPS Positioning Accuracy in Real-Time Navigation

Positioning accuracy is a challenging issue for location-based applications using a low-cost global positioning system (GPS). This paper presents an effective approach to improving the positioning accuracy of a low-cost GPS receiver for real-time navigation. The proposed method precisely estimates position by combining vehicle movement direction, velocity averaging, and distance between waypoints using coordinate data (latitude, longitude, time, and velocity) of the GPS receiver. The previously estimated precious reference point, coordinate translation, and invalid data check also improve accuracy. In order to evaluate the performance of the proposed method, we conducted an experiment using a GARMIN GPS 19xHVS receiver attached to a car and used Google Maps to plot the processed data. The proposed method achieved improvement of 4–10 meters in several experiments. In addition, we compared the proposed approach with two other state-of-the-art methods: recursive averaging and ARMA interpolation. The experimental results show that the proposed approach outperforms other state-of-the-art methods in terms of positioning accuracy

Graphene-based flexible textile supercapacitor for wearable electronic applications

Smart electronic textiles (e-textiles) have drawn significant interests as lightweight, flexible and comfortable next-generation wearable devices due to their ability to continuously monitor, collect, and communicate various physiological parameters. They hold promise for diverse applications, including sportswear, military uniforms, safety instruments, environmental monitoring, and healthcare applications. However, a key challenge in integrating wearable devices into textiles lies in the demand for lightweight, flexible, and high-performance power supply units. Consequently, thin and flexible textile-based supercapacitors are being explored due to their inherent lightweight nature and remarkable power density. Nonetheless, the manufacture of high-performance textile supercapacitors for widespread industrial adoption in a scalable manner remains a formidable challenge. To address this, the first study establishes an experimental protocol for traditional screen-printing of highly conductive graphene-based conductive inks on textiles showcasing their potential in applications like piezoresistive sensing, EEG electrodes, and supercapacitor electrodes. The resultant screen-printed in-plane textile supercapacitor achieves a notable aerial capacitance of approximately 3.2 mF cm-2. The second study focuses on the scalable exfoliations of two-dimensional materials, specifically graphene and MoS2, and their integration onto textiles using an industrially viable high-speed pad-dry-cure technique for high-performance wearable supercapacitors applications. The graphene-MoS2-graphene tri-layered heterostructure-based textile supercapacitors reveal an impressive areal capacitance of ~180 mF cm-2. In the third study, sustainable digital manufacturing of 2D heterostructure-based textiles was investigated via layer-by-layer inkjet printing of 2D materials (graphene, MoS2 and hBN) onto a rough and porous textile surface. The resulting graphene-hBN-graphene heterostructure textiles showcase a remarkable areal capacitance of ~32.5 mF cm-2, surpassing existing literature on graphene-based inkjet-printed supercapacitors. Finally, the fourth study explores the utilization of a standalone Co/Zn-metal organic framework (MOF) for textile supercapacitor applications employing screen printing, pad-dry-cure, and inkjet printing. The MOF-coated textiles achieve a remarkable areal capacitance of ~359.36 mF cm-2. The findings from these four studies distinctly highlight the promise of textile-based supercapacitors for wearable electronics applications, signifying an important step toward moving from R&D-based textile supercapacitors to actual real-world applications

PCA-based dimensionality reduction for face recognition

In this paper, we conduct a comprehensive study on dimensionality reduction (DR) techniques and discuss the mostly used statistical DR technique called principal component analysis (PCA) in detail with a view to addressing the classical face recognition problem. Therefore, we, more devotedly, propose a solution to either a typical face or individual face recognition based on the principal components, which are constructed using PCA on the face images. We simulate the proposed solution with several training and test sets of manually captured face images and also with the popular Olivetti Research Laboratory (ORL) and Yale face databases. The performance measure of the proposed face recognizer signifies its superiority

Phytochemical investigations of Campsis radicans L.

Petroleum ether, dichloromethane and ethyl acetate soluble fractions were obtained through partitioning the crude methanolic extract of the leaves of Campsis radicans L. (Family. Bignoniaceae) followed by the chromatographic separation of secondary metabolites from them. A total of five triterpene compounds i.e., corosolic acid methyl ester (1), β-amyrin (2), arjunolic acid (3), maslinic acid (4) and 28-O-[β-D-glucopyranosyl-(1→6)-β-D-glucopyranosyl]-2α,3α,19α-trihydroxy-12-en-28-ursolic acid (5) were isolated from the dichloromethane fractions and their structures were characterized by 1H NMR spectroscopy and compared the NMR data with published values